Ropinirole was developed as a dopamine agonist and is used for treatment of Parkinson's disease, and oral preparations of ropinirole are distributed in the market. There have been attempts to formulate ropinirole into patches (Patent Documents 1 and 2).
One advantage of the patches is that the preparations can be easily removed when a side effect occurs.
At present, ropinirole distributed in the market is its acid addition salt (specifically, ropinirole hydrochloride) because of its stability and handleability, and it is contemplated that transdermal absorption preparations are produced using the acid addition salt of ropinirole (Patent Document 3). However, generally, a transdermal absorption preparation using a drug in the form of acid addition salt has a drawback in that transdermal absorbability is much lower than that when a free drug (drug in free form) is used. When a dehydrochlorinating agent is used to convert the acid addition salt of ropinirole to free ropinirole within the preparation, the amount of the drug contained in the adhesive base is limited, and the acid addition salt is not completely converted to free ropinirole, so that transdermal absorbability may not be increased so much. In addition, a metal salt may precipitate in the adhesive base, causing problems such as deterioration of the physical properties of the patch and skin irritation by the metal salt.